Rattle from subwoofer

[Tommy108]

I recently began a build that has been plagued by nothing butt problems...im running 2 12" fu 300's a ppi p1000 amp and a box designed by shredder2...after finally getting everything together and finishing the box I must admit I was vaguely impressed with the bass output, however after about 3 weeks one sub has developed a strange rattle...only hear it in the higher bass notes the lows and really hard punchy bass sounds fine. So is the sub blown? If not any ideas what might be wrong?

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[THATpurpleKUSH 5,000+ posts]

Check all the glue on the sub, FU subs are known to become unglued. Are the subs wired correctly? It sounds like one could be out of phase. 

 

[Tommy108]

Yes they are wired to 1ohm final impedance...i have pulled both subs out of box and inspected them. I also tested them with a multimeter...voice coils of both subs still read 4ohm just like they should and I couldn't find anything wrong

 

[THATpurpleKUSH 5,000+ posts]

Try hooking up a different amp or different subs or 1 sub at a time. Also try playing the subs free air. Doing all of those tests will narrow down where the issue is coming from. Just out of curiosity, what are the specs on the box?

 

[Tommy108]

 

[Tommy108]

The box has been awesome...really sounded great for about 3 weeks now until this issue started

 

[THATpurpleKUSH 5,000+ posts]

Yea the box looks good, I doubt that is the problem. 

 

[hispls 5,000+ posts]

So let me get this straight, you're running 1000W to two 300W subs and you're wondering why one seems broken?

 

[Tommy108]

Yeah really sounded good...can't figure out what could've changed to cause the problem

 

[Tommy108]

So let me get this straight, you're running 1000W to two 300W subs and you're wondering why one seems broken?

Yeah that's right...the gain is not turned wide open only about halfway then the remote knob is turned down to even less...i don't see why I would be pushing to much power...and if it was blown I wouldn't think I would get a reading from the voice coil

 

[Tommy108]

Perhaps I've missed something  butt the majority of posts I've seen on here suggest a higher powered amp...the amp doesn't work as hard to push subs and you get less distotrion...or have I misunderstood this?

 

[blazian87 10+ year member]

Perhaps I've missed something  butt the majority of posts I've seen on here suggest a higher powered amp...the amp doesn't work as hard to push subs and you get less distotrion...or have I misunderstood this?

No you didn’t misunderstand that. Anyone would be better off with more power rather than less when it comes to distortion. The problem is setting your gains correctly. Just from reading your other post about your gains not turned wide open and only about half already tells me that you have your gains set too high. This largely depends on pre out voltage. You would never have the gain completely wide open unless you have the weakest signal ever. Half could very well be clipping too. Roughly 1/3 is where I usually set my gains at if I’m running a normal 4V aftermarket headunit. Even if your coils have a reading and your sub is not technically blown, doesn’t mean that it didn’t cause some damage to your sub. 

Also, where is your LPF set at right now? 

 

[shredder2]

Any way you could shoot a vid of said rattle so it's easier to understand? 

It might be easier to pinpoint if it's audible on a video... maybe

 

[Tommy108]

Lpf is set at 85 on hu somewhere close to that on amp...not sure if you'll be able to hear it on video or not butt I'll give it a try when the weather breaks here

 

[hispls 5,000+ posts]

Yeah that's right...the gain is not turned wide open only about halfway then the remote knob is turned down to even less...i don't see why I would be pushing to much power...and if it was blown I wouldn't think I would get a reading from the voice coil

So "gain" setting aside, (because it is meaningless).  Woofers have thermal and mechanical limits.  It sounds like yours has some mechanical failure.  Now you may be able to repair it or it may be a legitimate manufacturer defect, but if you're running double rated power to them it'll be hard to chalk it up to manufacturer defect IMO.